The present invention relates to internal combustion engines with multiple cylinders, of the type comprising:                at least one intake valve and at least one exhaust valve for each cylinder, each provided with respective elastic return means which bias the valve towards a closed position, to control respective intake and exhaust conduits,        at least one camshaft, to actuate the intake and exhaust valves of the engine cylinders by means of respective tappets,        in which at least each intake valve has variable actuation, being actuated by the respective tappet, against the action of the aforesaid elastic return means, by the interposition of hydraulic means including a pressurised fluid chamber, into which projects a pumping piston connected to the tappet of the intake valve,        said pressurised fluid chamber being able to be connected by means of a solenoid valve with an exhaust channel, in order to uncouple the variable actuation valve from the respective tappet and cause the rapid closure of the valve by effect of the respective elastic return means,        electronic control means for controlling each solenoid valve in such a way as to vary the time and travel of opening of the variable actuation valve as a function of one or more operative parameters of the engine,        in which the aforesaid hydraulic means further comprise an actuator unit for the variable actuation valve, which includes:        an actuating piston slidably mounted within a guide bushing,        said actuating piston facing a variable volume chamber communicating with the pressurised fluid chamber both through first communication means controlled by a check valve which allows only the passage of the fluid from the pressurised fluid chamber to the variable volume chamber, and through second communication means which allow the passage between the two chambers in both directions, and        hydraulic braking means able to cause a narrowing of said second communication means in the final phase of closure of the engine valve.        
An engine of the type specified above is described and illustrated for example in European patent application 1 344 900 A2 by the same Applicant.
In engines of this kind, it is very difficult to arrange all the elements of the variable valve control system without thereby increasing the size of the cylinder head with respect to a traditional engine.